Taking Care of an Oscar Fish, Its Tank, Water + Breeding

Scientifically known as the Astronotus ocellatus, Oscars are popular due to their playful behavior, intelligence, and attractive colorings. However, this fish requires more care, making it a suitable species for an average experienced aquarist.

There are 3 species of oscar fish: red, tiger & albino. They grow to 18 inches and for up to 20 years. They require 55 gallons per fish, 1-1.5 inches of substrate, high filtration water, natural light, decorations, pH of 6-8, and temperatures of 74-81°F. While clumsy, they’re very intelligent. 

Oscar Fish Care
Oscar Fish Care

How to take care of an Oscar

When keeping and caring for Oscars, you must learn how to set up their tanks and make them comfortable. Then check on cleaning intervals due to the fact that they release a lot of waste. Their diet should also be observed if you want them to remain healthy. Here is what to do:

1. Oscar fish tank setup

Due to their unique nature, oscar fish require special tank sizes and requirements. Here is everything you may need to know about oscar’s fish tank setup:

1. Tank size

For a healthy and clean aquarium, buying a 75-gallon tank for an Oscar, a 125-gallon for 2 Oscars, and a 150-200 gallons tank for 3 Oscars is recommended. This will be easier to maintain since a larger water body will experience a lower impact.

Due to their sheer size, Oscars require an appropriate tank for growth and survival. This is a suitable way to prevent unusual stress. Further, you should clean these tanks and check the water conditions frequently due to their unique messy characteristics.

2. Substrate

Gravel and sand are suitable substrates based on the suitable habitat for your Oscars. However, before stuffing your aquarium with these substrates, you should note that Oscars enjoy digging, taking in, and spitting substrates such as sand. This habit can easily damage the filters if the sand is projected at them.

If the substrate in a tank is sand, you can mitigate this problem by incorporating a pre-filter. This way, an Oscar can dig up and spit sand to its heart’s content, and you don’t have to worry about replacing the filter with a new one frequently.

If there is uneaten debris and food in the tank, it’ll sink after some time and act as a substrate. Thus, you should avoid adding too much substrate. Specifically, 1-1.5 inches of substrate is suitable if you use gravel.

3. Filtration

Oscars have high sensitivity to changes in water parameters and high levels of ammonia, unlike some types of fish that don’t need a water filter. Therefore, you require a durable filtration system to keep them healthy. 

In addition to their sensitivity, oscar fish is a highly messy fish with a high waste/bioload output. Thus, they require intensive water filtration, focusing on biofiltration.

A canister filter and a hang-on-back (HOB) filter, acting as a backup, will be sufficient for filtration. For the best results, choose a strong filtration system that can overturn the water volume in your aquarium at least 4 times each hour. 

4. Lighting

Oscar fish do not require special lighting. Keeping them in a typical room illuminated by daylight will produce excellent results. 

However, if you love adding fancy lights to your aquarium, they cannot harm your fish. Always keep in mind that most Oscars prefer moderate-low lighting. Therefore, you shouldn’t leave your aquarium bulb on for over 12 hours. Keeping the bulb on for longer hours will make your fish distressed and agitated. 

Suppose you are keeping Oscars that avoid intensive light. Consider removing your bulb or dimming it. Punch holes on a piece of paper and wrap the bulb using the foil to achieve dimming. Your bulb light will become dimmer with fewer holes.

5. Plants

Oscars prefer hiding against objects in the wild for their safety. The young enjoy living under ornaments and fake plants. That’s the only way to feel safe. Oscars are also known for their habit of rearranging their territories.

If there are live plants in the tank, Oscars can easily damage them since they will have more activities around them. Therefore, sturdy fake plants are suitable hiding places for them.

6. Decorations

Oscar fish have a habit of carrying/moving portable objects around in the aquarium. Therefore, avoid breakable decorations such as ceramic objects. Durable decorations like stone caves and PVC pipes suit your oscar fish tank.

Oscars are also known for their clumsy behavior of constantly moving around and crashing into items. Thus, always avoid adding decorations with rough textures and sharp edges in their habitat.

2. Water Conditions for Oscars

Since Oscars are highly sensitive to changes in water parameters, providing suitable water conditions for your oscar fish is essential. Missing these requirements can negatively affect and even become fatal. Therefore, always consider the following conditions:

1. Oscar Fish Temperature

Oscar fish thrive in the warm waters of the Amazon River Basin. Therefore, maintain a temperature of about 77°F in your aquarium and always ensure it lies between 74°F and 81°F at all times. 

2. Chlorine and Chloramines

All municipal water providers always add chlorine to kill bacteria. But is it safe for your oscar fish? Chlorine is a highly harmful gas to amphibians, mammals, and fish. Thus, you should avoid this gas and its compounds in their habitat/aquarium.

Always use a de-chlorinator before adding water to your fish tank. This removes chloramines, chlorine, and other metal traces from the water.

Here are some other essential rules you should follow to achieve the best results:

  • Never add water from your tap into your aquarium without dechlorinating it.
  • Oscar fish are highly sensitive to changes in water parameters. Thus, always dechlorinate water before adding it to your aquarium.
  • You can use a test kit to measure water quality to ensure you’ve removed all the chlorine compounds.

Basically, chlorine isn’t good for your Oscars and most other fish. Just like acclimating bettas or other aquarium pets is important, Always check the aquatic conditions when introducing Oscars to a new environment.

3. Water Flow

While in their natural habitats, Oscars live in low-flow, slow-moving white water, which provides them with suitable hiding spots from buzzards. This fish grows to a maximum length of 18 inches, with a fast monthly growth rate of 1 inch. 

Oscars enjoy low or moderated-high-flow waters identical to their natural habitat conditions. You should always aim to acquire a water turnover rate of 4 times each hour.

In other cases, your fish will be healthy and happy under high flow levels. Therefore, if your fish can swim comfortably under high water flows, the conditions are absolutely fine and most preferred.

4. Oscar water PH Level

Oscar fish love a water pH of around 7.2. You should always provide a stable pH between 6 and 8. 

Ensuring the right pH in your aquarium is essential since it can alter the toxicity level of ammonia in the water. This may, in turn, expose your fish to the risk of ammonia poisoning. 

If you notice a low pH in your aquarium, manipulate it using pH-changing kits and salts. However, avoid making fast, drastic changes.

3. Oscar fish tank mates

Typically, these fish perform best independently, but you can keep them with South American cichlids tankmates that aren’t too aggressive and passive. 

Expert aquarists regard oscar fish as mild-aggressive and territorial creatures. Oscars also bully each other, where smaller fish are the most probable victims.

Oscar fish tankmate species may include:

  • Green terrors
  • Jack Dempsey
  • Bichirs
  • Silver dollars
  • Convict cichlids
  • Firemouth cichlids
  • Severum cichlids
  • Arowana
  • Sailfinplecos

What fish to avoid keeping with oscars

Invertebrates and small fish, such as shrimp and crabs, are unsuitable tankmates for oscar fish. This is because oscar fish feed on fish that are smaller than them. 

4. What do Oscars eat?

Oscars enjoy eating smaller fish, insects, plants, worms, and all fruits in the wild. However, they will require a unique diet when kept in an aquarium. Cichlids eat strawberries, and Oascars are also scientifically classified in that group. That means Oscars will also enjoy this fruit.

Here is some helpful information you need to know about their food requirements:

1. Best foods for Oscars

When keeping Oscars in your aquarium, always aim to replicate their wild diet as much as possible. You should supply your oscar fish with a quality, protein-rich diet ranging from frozen and processed to freeze-dried foods.

A protein-rich commercial fish food manufactured for carnivorous species (e.g., cichlid pellets) can be enough. They constitute 80% of your oscar’s nutritional requirements. 

In addition, always supplement your oscars’ diet with live natural food, including locusts, crickets, grasshoppers, and mealworms.

2. Foods to avoid

Avoid feeding your oscar fish live feeder fish. These can transfer diseases and parasites that may impair your oscars and the aquarium environment. However, if you feed your oscars with live feeder fish, always confirm they are healthy and high-quality species.

3. How often should oscars be fed?

Young oscar fish are greedy eaters and may seem hungry at all times. However, you should limit their dietary intake as overfeeding can trigger illness. Thankfully, here are applicable ways to achieve this:

  • Feed your baby Oscars with 3-4 pellets at the beginning. Immerse them and allow your oscar to eat them, then later add more.
  • Follow this pattern for about three minutes and stop. Add more once your oscar has completed eating all the pellets.
  • Follow these steps about 2-3 times daily and remove any leftovers within 2-3 minutes to prevent altering the water quality.

Your young oscars may appear full but seem to demand more food. Avoid temptations to supply them with additional food than their requirements.

After your oscar attains 5 inches, you should change its feeding patterns. At this stage, you should feed them twice daily. 

You can also add other food supplements, such as grasshoppers and mealworms, in their meals. Follow this routine during your oscar fish adulthood. It is also okay to drop 2-4 slices of cucumber in the tank for nutrition and cleansing.

5. Breeding

Breeding oscar fish is a possible but demanding task. Oscars are choosy when selecting their mates. Also, mates must mature at 16 months to 2 years for reproduction. Fortunately, you can breed various breeds of oscars; red, tiger, or albino.

1. Breeding Procedure

Oscars prefer breeding during rainy seasons when growing in the wild. You can easily incorporate these conditions in your aquarium by changing 20-30% of the water after every two days. Similarly, you can drastically reduce the water temperature by a few degrees to make the conditions favorable.

Finally, sprinkle dechlorinated water using a watering can above your aquarium for about 5-10 minutes multiple times daily. 

You can also consider installing filter spray bars above your aquarium water level to replicate these conditions if you are too busy to carry out the tasks manually.

2. Sexing oscars

Males have one sharp spike for fertilization, while females have an egg tube fully retracting inside them. 

Sexing oscar fish is a demanding task. These monomorphic fish make it hard to differentiate between males and females. However, multiple characteristics can be easily discovered in the male and female genitals.

Oscar fish Problems and their solutions

Oscar fish rarely get ill, but they are at a high risk of catching some illnesses. Here are the most common diseases affecting them and their solutions:

  • Hole in the head disease: This disease can be identified with signs of holes and cavities across the fish’s body and head. It is mainly caused by a deficiency of nutrients and can be easily managed by feeding them a suitable diet, as discussed above. This is one of the many reasons why fish die if left untreated.
  • Bacteria: Oscar fish can easily get ill when fed live feeder fish containing bacteria. You can easily minimize this risk by quarantining the live feeder fish before using them as an oscar fish diet.

Preventing these illnesses isn’t a big problem if you stick to the normal care routine for most fish types.

Oscar fish care


With the scientific name Astronotus ocellatus, oscar fish is a cichlid family fish species originating from South America. It’s an indigenous species of many countries, including Columbia, Brazil, Peru, and Ecuador. However, it is commonly found in the Amazon River Basin.

Types of Oscars
Types of Oscars

Adult Oscars appear dark with spots of yellow bands on their fins, and their young ones bear orange and white stripes until adolescence.

Scientific nameAstronotus ocellatus
Life expectancy15-20 years
Size 10-12 inches (monomorphic)
Diet Omnivore 
Tank size55 gallons per fish
Temperatures 74-78°F (23-27°C)
Water hardness5-20dGH
Breeds Red, tiger, albino
Substrate 1-1.5 inches
Water filtration4-hour complete filtration cycle
Lighting Natural, dim light
Plants Sturdy, fake plants
Tank matesGreen terrors, bichris, arowana
About Oscars

Generally, Oscars can live longer in your aquarium under the right habitat conditions. Choose the right room, install a durable filtration system, and provide the right diet for them.

References and sources for this article include the University of Michigan. Astronotus ocellatus: Marble cichlid, The University of Michigan. Cichlidae: Cichlids and Florida Museum under Astronotus ocellatus.

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